Controllers/SongsViewController.m

/*
     File: SongsViewController.m
 Abstract: Lists all songs in a table view. Also allows sorting and grouping via bottom segmented control.
  Version: 1.4
 
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 */
 
#import "SongsViewController.h"
#import "SongDetailsController.h"
#import "Song.h"
 
@interface SongsViewController ()
 
@property (nonatomic, strong) SongDetailsController *detailController;
@property (nonatomic, strong) NSFetchedResultsController *fetchedResultsController;
@property (nonatomic, strong) IBOutlet UISegmentedControl *fetchSectioningControl;
 
@end
 
 
#pragma mark -
 
@implementation SongsViewController
 
- (void)viewDidLoad {
    
    [super viewDidLoad];
    [self fetch];   // start fetching songs from our data store
}
 
- (IBAction)changeFetchSectioning:(id)sender {
    
    self.fetchedResultsController = nil;
    [self fetch];
}
 
- (void)fetch {
    
    NSError *error = nil;
    BOOL success = [self.fetchedResultsController performFetch:&error];
    NSAssert2(success, @"Unhandled error performing fetch at SongsViewController.m, line %d: %@", __LINE__, [error localizedDescription]);
    [self.tableView reloadData];
}
 
- (NSFetchedResultsController *)fetchedResultsController {
    
    if (_fetchedResultsController == nil) {
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        [fetchRequest setEntity:[NSEntityDescription entityForName:@"Song" inManagedObjectContext:self.managedObjectContext]];
        NSArray *sortDescriptors = nil;
        NSString *sectionNameKeyPath = nil;
        if ([self.fetchSectioningControl selectedSegmentIndex] == 1) {
            sortDescriptors = [NSArray arrayWithObjects:[[NSSortDescriptor alloc] initWithKey:@"category.name" ascending:YES], [[NSSortDescriptor alloc] initWithKey:@"rank" ascending:YES], nil];
            sectionNameKeyPath = @"category.name";
        } else {
            sortDescriptors = [NSArray arrayWithObject:[[NSSortDescriptor alloc] initWithKey:@"rank" ascending:YES]];
        }
        [fetchRequest setSortDescriptors:sortDescriptors];
        _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                                                        managedObjectContext:self.managedObjectContext
                                                                          sectionNameKeyPath:sectionNameKeyPath
                                                                                   cacheName:nil];
    }    
    return _fetchedResultsController;
}    
 
 
#pragma mark - UITableViewDataSource
 
- (NSInteger)numberOfSectionsInTableView:(UITableView *)table {
    
    return [[self.fetchedResultsController sections] count];
}
 
- (NSInteger)tableView:(UITableView *)table numberOfRowsInSection:(NSInteger)section {
    
    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
    return [sectionInfo numberOfObjects];
}
 
- (NSString *)tableView:(UITableView *)table titleForHeaderInSection:(NSInteger)section {
    
    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
    if ([self.fetchSectioningControl selectedSegmentIndex] == 0) {
        return [NSString stringWithFormat:NSLocalizedString(@"Top %d songs", @"Top %d songs"), [sectionInfo numberOfObjects]];
    } else {
        return [NSString stringWithFormat:NSLocalizedString(@"%@ - %d songs", @"%@ - %d songs"), [sectionInfo name], [sectionInfo numberOfObjects]];
    }
}
 
- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)table {
    
    // return list of section titles to display in section index view (e.g. "ABCD...Z#")
    return [self.fetchedResultsController sectionIndexTitles];
}
 
- (NSInteger)tableView:(UITableView *)table sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index {
    
    // tell table which section corresponds to section title/index (e.g. "B",1))
    return [self.fetchedResultsController sectionForSectionIndexTitle:title atIndex:index];
}
 
- (UITableViewCell *)tableView:(UITableView *)table cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *kCellIdentifier = @"SongCell";
    
    UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:kCellIdentifier forIndexPath:indexPath];
    Song *song = [self.fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = [NSString stringWithFormat:NSLocalizedString(@"#%d %@", @"#%d %@"), [song.rank integerValue], song.title];
    
    return cell;
}
 
 
#pragma mark - Segue support
 
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    
    if ([[segue identifier] isEqualToString:@"showDetail"]) {
        
        SongDetailsController *detailsController = (SongDetailsController *)[segue destinationViewController];
        NSIndexPath *selectedIndexPath = [self.tableView indexPathForSelectedRow];
        detailsController.song = [self.fetchedResultsController objectAtIndexPath:selectedIndexPath];
    }
}
 
@end